This invention relates to an intake system for a multi-cylinder internal-combustion engine operating with exhaust-gas recirculation and fuel injection, particularly an air-compressing injection internal-combustion engine having an air-guiding casing for guiding or mixing clean air and recirculated exhaust gases to be supplied to the engine intake connections.
It has been contemplated to provide that, in order to achieve a better exhaust gas quality, recirculated exhaust gas is furnished to the combustion air flow in certain load ranges of the multi-cylinder internal-combustion engine. In the case of the intake system according to German Pat. No. (DE-PS) 3 324 343, corresponding to commonly assigned co-pending U.S. patent application Ser. No. 627,666, filed July 3, 1984, now U.S. Pat. No. 4,640,256, a mixing duct that is separated from the distributor volume is provided in a compactly constructed air-guiding casing, the mixing path of said mixing duct, in the case of the exhaust gas recirculation, having the purpose of causing a good mixing of the furnished exhaust gases with the combustion air before the entering of same into the distributor volume space.
This invention is based on the objective of developing a compactly constructed air-guiding casing of the above-mentioned type by means of simple constructional measures on the inside of the casing to the extent that a better mixing of the exhaust gas with the combustion air and subsequently a more even distribution of the air-exhaust gas mixture at the individual cylinders of the internal-combustion engine can be achieved.
The objective according to the invention is achieved by providing a throttle valve disposed centrally of the mixing duct means for communicating clean air to the mixing duct, with exhaust gas supply surrounding the throttle valve.
By means of the measures according to especially preferred embodiments of the invention, in the case of the exhaust-gas recirculating operation, because of the special position of the exhaust gas inlet into the mixing duct as well as by means of the special assignment of this inlet in the direction of the air inlet, an optimal mixing of the exhaust gases with the combustion air is achieved. In addition, by means of the special arrangement of the air throttle valve in the wall part of the partition as well as by means of the air-exhaust gas transfer points that are arranged symmetrically between the mixing duct and the distributor volume, a more even distribution of the mixture on the individual cylinders is achieved while maintaining a high volumetric efficiency. The exhaust gas quality of multi-cylinder internal-combustion engines is improved in this way.
In the case of the air-guiding casing according to DE-PS No. 3 324 343, there is an orientation in the mixing duct of the exhaust gas inlet to the air inlet, said orientation, in order to achieve an almost homogeneous air-exhaust gas mixture, requiring a long mixing path. As a result, locally unfavorable overflow cross-sections occur from the mixing duct to the distributor volume because of which an even distribution of the mixture on the individual cylinders cannot be achieved to the desirable extent.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment/several embodiments in accordance with the present invention.